The invention relates to an oto-acoustic emission analyser.
Such an apparatus is used for audiometric emission measurements on an individual, e.g. a person whose hearing ability is to be examined. Emission-like measurements are discussed for the first time in Danish patent no. 147,726 (U.S. Pat. No. 4,374,526), in which the British researcher D. T. Kemp deals with the measurement of echo signals from a person's inner ear, i.e. measuring of an acoustic echo brought about by introducing an acoustic signal in the form of a transient audio signal into the ear by means of a transducer. This measuring technique has since been further developed, and it has now become apparent that what is involved is not an echo but a stimulated emission from the inner ear. It has subsequently been ascertained that the emission can be stimulated in other ways, e.g. by using tone pairs, so-called stimulus signals, which consist of two or more pairs of substantially sinusoidal oscillations, these pairs having frequencies which lie relatively close to each another, e.g. so that one signal has a frequency in the range of 1.2 times the other frequency. This technique is described, for example, in international application no. WO 93/20746. Others have developed other signal combinations which can also stimulate the inner ear to provide measurable emission signals.
As a minimum, an emission measurement thus requires a measuring probe to be introduced into the ear of the person on whom the measurement is to be carried out, said probe comprising at least one, or preferably two, transducers for the generation of stimulus signals, and at least one transducer for measurement of the emission signal, plus an associated electronic circuit, partly for the generation of the signals and partly for the processing of the emission signals. Equipment of this kind has hitherto been produced as table-type apparatus of a certain size, to which a long cable is connected. One end of the cable is connected to the table apparatus, and the other end of the cable is connected to a probe unit with a measuring probe. For example, such an apparatus is depicted and explained in Danish patent application no. 393/93, which is owned by the applicant of the present application. Such table-type equipment can carry out the desired measurements, but it is required that the person or the individual to be measured is brought to the equipment, which can often be inexpedient. It is particularly inexpedient if systematic measurements, so-called screening, are to be carried out on a certain group of the population, e.g. new-born babies. Table-type equipment with cable and measuring probe also often suffers the disadvantage that a calibration is required if the probe is replaced.
Other types of audiometric apparatus are known for the screening of a population group, where the apparatus is portable, e.g. carried in the hand. A hand-held tympanometer, i.e. an apparatus for measuring the acoustic impedance in the outer ear under varying pressure conditions, is known from U.S. Pat. No. 4,688,582. However, such an apparatus provides only limited information concerning the person's possible hearing ailment. Consequently, there is a need for an apparatus which can carry out more detailed measurements and thereby provide a considerably better sceening result.